Mundet Bernat, Hartman Steven T, Guzman Roger, Idrobo Juan C, Obradors Xavier, Puig Teresa, Mishra Rohan, Gázquez Jaume
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193 Barcelona, Spain.
Institute of Materials Science and Engineering, Washington University in St Louis, St Louis, Missouri 63130, USA.
Nanoscale. 2020 Mar 12;12(10):5922-5931. doi: 10.1039/d0nr00666a.
It is well known that in the high-temperature superconductor YBa2Cu3O7-x (YBCO), oxygen vacancies (VO) control the carrier concentration, its critical current density and transition temperature. In this work, it is revealed that VO also allows the accommodation of local strain fields caused by large-scale defects within the crystal. We show that the nanoscale strain associated with Y2Ba4Cu8O16 (Y124) intergrowths-that are common defects in YBCO-strongly affect the venue and concentration of VO. Local probe measurements in conjunction with density-functional-theory calculations indicate a strain-driven reordering of VO from the commonly observed CuO chains towards the bridging apical sites located in the BaO plane and bind directly to the superconducting CuO2 planes. Our findings have strong implications on the physical properties of the YBCO, as the presence of apical VO alters the transfer of carriers to the CuO2 planes, confirmed by changes in the Cu and O core-loss edge probed using electron energy loss spectroscopy, and creates structural changes that affect the Cu-O bonds in the superconducting planes. In addition, the revelation of apical VO also has implications on modulating critical current densities and enhancing vortex pinning.
众所周知，在高温超导体钇钡铜氧（YBCO）中，氧空位（VO）控制着载流子浓度、临界电流密度和转变温度。在这项工作中，研究发现VO还能够容纳由晶体中的大规模缺陷引起的局部应变场。我们表明，与Y2Ba4Cu8O16（Y124）共生相关的纳米级应变（Y124是YBCO中常见的缺陷）强烈影响VO的位置和浓度。结合密度泛函理论计算的局部探针测量表明，VO由通常观察到的CuO链向位于BaO平面的桥接顶端位点发生应变驱动的重新排列，并直接与超导CuO2平面结合。我们的发现对YBCO的物理性质有重大影响，因为顶端VO的存在改变了载流子向CuO2平面的转移，这通过使用电子能量损失谱探测的Cu和O芯损失边缘的变化得到证实，并产生了影响超导平面中Cu - O键的结构变化。此外，顶端VO的发现对调节临界电流密度和增强涡旋钉扎也有影响。
